The present invention refers to a pressure measuring instrument comprising a mounting plate and a flexible separating element which is disposed in an opening of the mounting plate and fastened thereto, the separating element being under the action of a measured pressure during the pressure measurement.
In pressure measuring instruments of the above-mentioned kind, the pressure acting e.g. on a membrane is usually measured by measuring the corresponding force acting upon the membrane by means of a force-sensing element which delivers a signal whose amplitude corresponds to the measured pressure. Pressure measuring instruments of this kind exhibit an undesired sensitivity to accelerations since the membrane which is exposed to the pressure and the measuring element itself have a certain mass. Therefore, in the case of accelerations of the entire pressure measuring instrument in the axial direction, the force-sensing element is not only subject to the pressure force to be measured but also to a force of inertia which is superimposed on the pressure force. The measured pressure signal is therefore incorrect.
Pressure measuring instruments are known in which two measuring elements are used in order to compensate the influence of accelerations on the measuring result, the two measuring elements having the same sensitivity to acceleration, but only one of them being exposed to the pressure to be measured. In other words, a pressure measuring element and an acceleration measuring element are used. In such pressure measuring instruments, the error of the measuring result on account of the acceleration is corrected by forming the difference of the signals delivered by the measuring elements.
These known pressure measuring instruments have the disadvantage that two distinct measuring elements are required, thereby increasing the manufacturing costs. Moreover, the two distinct measuring elements mostly have different basic sensitivities and therefore have to be balanced.
Generally, the used measuring elements also have different temperature characteristics and frequency responses. The obtained compensation therefore usually depends on the frequency and the temperature.
Consequently, the aim of the invention is to provide a pressure measuring instrument of the above-mentioned kind comprising a single measuring element which is mounted in such a manner that the influence of accelerations is compensated while the acceleration compensation is largely independent from the temperature characteristics, the frequency response, and the aging of the measuring instrument.
According to the invention, this aim is attained by a pressure measuring instrument of the above-mentioned kind wherein the pressure measuring instrument further comprises a reference body which is connected to said mounting plate via a suspension and comprises a reference surface facing a surface of said separating element, the reference body and the suspension being so designed that when the entire pressure measuring instrument is under the action of an acceleration, the resulting displacement of the reference surface of said reference body is equal to the displacement of the surface of said separating element on account of the acceleration.
In particular, the advantages provided by a pressure measuring instrument according to the invention are that acceleration compensated measuring results, which are largely independent from the temperature characteristics, the frequency response, and the aging of the measuring element, are obtained substantially without increasing the manufacturing costs.